[英]Hibernate Entity OneToOne with same Primary and Foreign Key Bidirectional Relationship
[英]Making primary key same as foreign key in Hibernate entity
我是 Hibernate 的新手。 我正在研究两个实体,如下所示:
实体 1 如下:
@Entity
@Table(name = "vm_user")
public class VmUser implements Serializable {
private static final long serialVersionUID = 1L;
@Column(name = "created_by")
private String createdBy;
@Column(name = "last_modified_by")
private String lastModifiedBy;
@Column(name = "created_date")
private Instant createdDate;
@Column(name = "last_modified_date")
private Instant lastModifiedDate;
@OneToOne
@JoinColumn(unique = true)
private User user; <--- HOW WILL I DENOTE THIS PRIMARY KEY OF VMUSER ENTITY ?
在 mysql 的关联表中,即vm_user
中, user_id
既是主键,也是外键,指的是与User
实体关联的user
表的 id。
实体 2 如下:
@Entity
@Table(name = "my_entity")
public class MyEntity implements Serializable {
private static final long serialVersionUID = 1L;
@Column(name = "created_by")
private String createdBy;
@Column(name = "last_modified_by")
private String lastModifiedBy;
@Column(name = "created_date")
private Instant createdDate;
@Column(name = "last_modified_date")
private Instant lastModifiedDate;
@ManyToOne
private A a;
@OneToOne
@JoinColumn(unique = true)
private B b;
在 mysql 即my_entity
的关联表中,主键是 a 的id of a
和id of b
的 id 的组合。 我不知道如何在 Hibernate 实体MyEntity
中表示这一点。
关于同样的,我经历了一些帖子: Hibernate foreign key as part of primary key和JPA & Hibernate - Composite primary key with foreign key ,但不知道如何做这两个?
解决方案是@MapsId
例如
@Entity
@Table(name = "vm_user")
public class VmUser implements Serializable {
@Id
@Column(name = "user_id")
private Integer id;
@MapsId
@OneToOne
private User user;
您还可以删除@JoinColumn(unique = true)
,因为@Id
已经使其独一无二。
public class MyEntityPk implements Serializable {
private Integer aId;
private Integer bId;
// IMPORTANT: Override equals() and hashCode()
}
@IdClass(MyEntityPk.class)
@Entity
@Table(name = "my_entity")
public class MyEntity implements Serializable {
@Id
private Integer aId;
@Id
private Integer bId;
@MapsId("aId")
@ManyToOne
private A a;
@MapsId("bId")
@OneToOne
private B b;
请在 Hibernate 文档中找到更多信息https://docs.jboss.org_hibernate/orm/5.4/userguide/html_shtmlidentifier-derived_Guide
您需要使用@EmbeddedId
和@MapsId
,
@Entity
@Table(name = "vm_user")
public class VmUser implements Serializable {
@Id
@Column(name = "user_id")
private Integer id;
@MapsId("user_id")
@OneToOne
private User user;
}
您可以对 MyEntity 执行相同的操作,如下所示,
@Embeddable
class BKey {
private int aId;
private int bId;
}
@Entity
@Table(name = "my_entity")
public class MyEntity implements Serializable {
@EmbeddedId
private BKey primaryKey;
@MapsId("aId")
@ManyToOne
private A a;
@MapsId("bId")
@OneToOne
@JoinColumn(unique = true)
private B b;
}
虚拟机用户 class
public class VmUser implements Serializable {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;
@OneToOne
@JoinColumn(name="ID")
private Users user;
用户 class
public class Users implements Serializable {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;
@OneToOne(mappedBy="user")
private VmUser vmUser;
一个class
@Entity
public class A implements Serializable {
@Id
private long id;
@OneToMany(mappedBy="a")
private List<MyEntity> myEntitys;
B Class
@Entity
public class B implements Serializable {
@Id
private long id;
@OneToMany(mappedBy="b")
private List<MyEntity> myEntitys;
我的实体 class
@Entity
public class MyEntity implements Serializable {
private static final long serialVersionUID = 1L;
@EmbeddedId
private MyEntityPK id;
@ManyToOne
@JoinColumn(name="ID1")
private A a;
@ManyToOne
@JoinColumn(name="ID2")
private B b;
MyEntityPK class
@Embeddable
public class MyEntityPK implements Serializable {
@Column(insertable=false, updatable=false)
private long id1;
@Column(insertable=false, updatable=false)
private long id2;
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